Influence of serum and polystyrene plate type on stability of Candida albicans biofilms

Aqueous spice extracts as alternative antimycotics to control highly drug resistant extensive biofilm forming clinical isolates of Candida albicans

Candida albicans form biofilm by associating with biotic and abiotic surfaces. Biofilm formation by C. albicans is relevant and significant as the organisms residing within, gain resistance to conventional antimycotics and are therefore difficult to treat. This study targeted the potential of spice-based antimycotics to control C. albicans biofilms. Ten clinical isolates of C. albicans along with a standard culture MTCC-3017 (ATCC-90028) were screened for their biofilm-forming ability. C. albicans M-207 and C. albicans S-470 were identified as high biofilm formers by point inoculation on Trypticase Soy Agar (TSA) medium as they formed a lawn within 16 h and exhibited resistance to fluconazole and caspofungin at 25 mcg and 8 mcg respectively. Aqueous and organic spice extracts were screened for their antimycotic activity against C. albicans M-207 and S-470 by agar and disc diffusion and a Zone of Inhibition was observed. Minimal Inhibitory Concentration was determined based on growth absorbance and cell viability measurements. The whole aqueous extract of garlic inhibited biofilms of C. albicans M-207, whereas whole aqueous extracts of garlic, clove, and Indian gooseberry were effective in controlling C. albicans S-470 biofilm within 12 h of incubation. The presence of allicin, ellagic acid, and gallic acid as dominant compounds in the aqueous extracts of garlic, clove, and Indian gooseberry respectively was determined by High-Performance Thin Layer Chromatography and Liquid Chromatography-Mass Spectrometry. The morphology of C. albicans biofilm at different growth periods was also determined through bright field microscopy, phase contrast microscopy, and fluorescence microscopy. The results of this study indicated that the alternate approach in controlling high biofilm-forming, multi-drug resistant clinical isolates of C. albicans M-207 and S-470 using whole aqueous extracts of garlic, clove, and Indian gooseberry is a safe, potential, and cost-effective one that can benefit the health care needs with additional effective therapeutics to treat biofilm infections.

Study of the impact of cultivation conditions and peg surface modification on the in vitro biofilm formation of Staphylococcus aureus and Staphylococcus epidermidis in a system analogous to the Calgary biofilm device

Introduction. Staphylococcus aureus (SA) and Staphylococcus epidermidis (SE) are the most common pathogens from the genus Staphylococcus causing biofilm-associated infections. Generally, biofilm-associated infections represent a clinical challenge. Bacteria in biofilms are difficult to eradicate due to their resistance and serve as a reservoir for recurring persistent infections.Gap Statement. A variety of protocols for in vitro drug activity testing against staphylococcal biofilms have been introduced. However, there are often fundamental differences. All these differences in methodical approaches can then be reflected in the form of discrepancies between results.Aim. In this study, we aimed to develop optimal conditions for staphylococcal biofilm formation on pegs. The impact of peg surface modification was also studied.Methodology. The impact of tryptic soy broth alone or supplemented with foetal bovine serum (FBS) or human plasma (HP), together with the impact of the inoculum density of bacterial suspensions and the shaking versus the static mode of cultivation, on total biofilm biomass production in SA and SE reference strains was studied. The surface of pegs was modified with FBS, HP, or poly-l-lysine (PLL). The impact on total biofilm biomass was evaluated using the crystal violet staining method and statistical data analysis.Results. Tryptic soy broth supplemented with HP together with the shaking mode led to crucial potentiation of biofilm formation on pegs in SA strains. The SE strain did not produce biofilm biomass under the same conditions on pegs. Preconditioning of peg surfaces with FBS and HP led to a statistically significant increase in biofilm biomass formation in the SE strain.Conclusion. Optimal cultivation conditions for robust staphylococcal biofilm formation in vitro might differ among different bacterial strains and methodical approaches. The shaking mode and supplementation of cultivation medium with HP was beneficial for biofilm formation on pegs for SA (ATCC 29213) and methicillin-resistant SA (ATCC 43300). Peg conditioning with HP and PLL had no impact on biofilm formation in either of these strains. Peg coating with FBS showed an adverse effect on the biofilm formation of these strains. By contrast, there was a statistically significant increase in biofilm biomass production on pegs coated with FBS and HP for SE (ATCC 35983).

Amphotericin B, fluconazole, and nystatin as development inhibitors of Candida albicans biofilms on a dental prosthesis reline material: Analytical models in vitro

STATEMENT OF PROBLEM

The use of antifungals has been suggested during the treatment of denture stomatitis associated with Candida albicans biofilms. However, how time, material surface, and substrates present during adhesion and biofilm development can influence clinical treatment is unclear.

PURPOSE

The purpose of this in vitro study was to investigate the growth kinetics of C. albicans biofilms on surfaces of specimens under the influence of adsorbed films and to evaluate the antibiofilm efficacy of antifungal agents: amphotericin B, fluconazole, and nystatin.

MATERIAL AND METHODS

Specimens of Silagum-Comfort Soft Relining were submerged in preconditioning systems: phosphate-buffered saline, artificial saliva, fetal bovine serum, and artificial saliva+fetal bovine serum. Planktonic cells were incubated (phosphate-buffered saline+specimens) for 1.5 hours (adhesion phase) and washed with phosphate-buffered saline solution. The specimens were then incubated (YNB+glucose) for 8, 24, and 48 hours (initial, intermediate, and maturation phases). The biofilm sessile minimum inhibitory concentration was determined by the broth microdilution method (7.81 to 500 μg/mL). The metabolic activity of the biofilms was tested by colorimetric assay (cell metabolic activity). Cell viability, relative biomass (μm³), and the thickness of the biofilm (μm) were evaluated by confocal laser scanning microscopy.

RESULTS

The highest bioactivity was recorded in the presence of fetal bovine serum. Biofilms treated with fluconazole and amphotericin B were partially inhibited in a dose-dependent manner. Nystatin inhibited metabolic activity mainly from ≥15.63 or 62.5 μg/mL. Variations in magnitude parameters (relative biomass and thickness) were observed depending on the development phases of biofilms, whereas biological parameters (percentage of nonviable cells) were constant throughout the formation of C. albicans biofilms.

CONCLUSIONS

The data suggest that partial (fluconazole and amphotericin B) or more effective (nystatin) reduction of metabolic activity of C. albicans biofilms occurred depending on the time and the antifungal and its concentrations.

Biofilm inhibiting properties of compounds from the leaves of Warburgia ugandensis Sprague subsp ugandensis against Candida and staphylococcal biofilms

ETHNOPHARMACOLOGICAL RELEVANCE

Warburgia ugandensis Sprague subspecies ugandensis is a plant widely distributed in Eastern, Central and Southern Africa. In humans, it is used to treat respiratory infections, tooth aches, malaria, skin infections, venereal diseases, diarrhea, fevers and aches.

AIM OF THE STUDY

This study aims to identify the bioactive compounds against clinically important biofilm-forming strains of Candida and staphylococci that are responsible for tissue and implanted device-related infections.

METHODS

Using a bioassay-guided fractionation approach, hexane -, ethanol -, acetone - and water extracts from the leaves of W. ugandensis, their subsequent fractions and isolated compounds were tested against both developing and preformed 24 h-biofilms of Candida albicans SC5314, Candida glabrata BG2, Candida glabrata ATCC 2001, Staphylococcus epidermidis 1457 and Staphylococcus aureus USA 300 using microtiter susceptibility tests. Planktonic cells were also tested in parallel for comparison purposes. Confocal scanning laser microscopy was also used to visualize effects of isolated compounds on biofilm formation.

RESULTS

Warburganal, polygodial and alpha-linolenic acid (ALA) were the major bioactive compounds isolated from the acetone extract of W. ugandensis. For both warburganal and polygodial, the biofilm inhibitory concentration that inhibits 50% of C. albicans developing biofilms (BIC50) was 4.5 ± 1 and 10.8 ± 5 μg/mL respectively. Against S. aureus developing biofilms, this value was 37.9 ± 8 μg/mL and 25 μg/mL with warburganal and ALA respectively. Eradication of preformed 24 h biofilms was also observed. Interestingly, synergy between the sesquiterpenoids and azoles against developing C. albicans biofilms resulted in an approximately ten-fold decrease of the effective concentration required to completely inhibit growth of the biofilms by individual compounds. The hydroxyl group in position C-9 in warburganal was identified as essential for activity against staphylococcal biofilms. We also identified additional promising bioactive sesquiterpenoids; drimenol and drimendiol from the structure-activity relationship (SAR) studies.

CONCLUSIONS

ALA and four sesquiterpenoids: polygodial, warburganal, drimenol and drimendiol, have shown biofilm-inhibitory activity that has not been reported before and is worth following up. These compounds are potential drug candidates to manage biofilm-based infections, possibly in combination with azoles.

Does the composition of polystyrene trays affect Candida spp. biofilm formation?

The biofilm formation ability of Candida species seems to have a role in the prognosis of patients with candidemia. Biofilm formation is usually tested using 96 well flat bottom polystyrene microtiter plates, although the type of plastic used is not commonly reported. This study compares biofilm formation by Candida spp. on six types of plates from three brands (three non-tissue-treated and three tissue-treated). Thirty isolates of each of the following species were selected: C. albicans, C. parapsilosis, C. glabrata, C. tropicalis, as well as 15 isolates of C. krusei (n = 135 isolates) from patients with candidemia. Biofilm production was evaluated by measuring biomass production and metabolic activity. Our results show higher biomass production and metabolic activity of biofilms formed on non-tissue-treated plates in comparison to those formed on tissue-treated plates (P < .001). We only found significant differences in metabolic activity of biofilms formed on non-tissue-treated plates (P < .003). All comparisons including biofilm formation and metabolic activity among plates of the same brand yielded higher biofilm formation on non-treated plates compared to treated plates (P < .001). Significant difference in biomass production by C. parapsilosis was only seen when comparing between the various tissue-treated plastics (P < .03). In contrast, comparisons of different non-tissue-treated tray brands yielded significant metabolic activity differences for all species except for C. parapsilosis (P < .05). Biofilm formation and metabolic activity is significantly affected by the plastic composition of non-tissue-treated trays leading to increased biofilm formation.

Bioassay-Guided Isolation of Anti-Candida Biofilm Compounds From Methanol Extracts of the Aerial Parts of Salvia officinalis (Annaba, Algeria)

Salvia officinalis is frequently used in traditional Algerian medicine to treat diverse microbial infections, including oral and vaginal candidiasis. The aerial parts of S. officinalis collected in Annaba, Algeria were extracted in parallel by maceration with four solvents viz. hexane, acetone, methanol and water. All the extracts were tested in vitro against several Candida species: C. albicans, C. glabrata, and C. parapsilosis. Furthermore, the activity against biofilm-forming C. albicans was investigated using bioassay-guided fractionation. A large-scale extract was prepared via maceration in methanol, followed by fractionation on a silica gel column using increasingly polar mixtures of n-hexane, ethyl acetate, methanol, and acetic acid as mobile phase, to yield a total of 150 fractions. Two major active fractions (F-31 and F-39), were further separated by HPLC, resulting in several active chromatographic peaks. Carnosol and 12-methoxy-trans-carnosic acid were isolated as two major active compounds, and identified by a combination of NMR and mass spectrometry. The biofilm inhibitory concentration showed that 12-methoxy-trans-carnosic acid is more effective than carnosol with BIC50 values of 94 μM (95% confidence interval, 78.9-112.1 μM) and 314 μM (95% confidence interval, 200.7-491.2 μM), respectively. The present study supports the traditional use of sage in the treatment of various fungal infections caused by Candida. Further studies of the bioactive compounds in an in vivo Candida biofilm model are required to validate their clinical potential as antifungals.

Fungal-Host Interaction: Curcumin Modulates Proteolytic Enzyme Activity of Candida albicans and Inflammatory Host Response In Vitro

Current treatments for Candida albicans infection are limited due to the limited number of antifungal drugs available and the increase in antifungal resistance. Curcumin is used as a spice, food preservative, flavoring, and coloring agent that has been shown to have many pharmacological activities. Thus, this study evaluated the modulatory effects of curcumin on major virulence factors associated with the pathogenicity of C. albicans. The minimum inhibitory concentration (MIC) of curcumin against C. albicans (SC5314) was determined. Biofilm formation was quantified and the proteinase and phospholipase secretion was measured. The cytotoxicity was tested in oral fibroblast cells. A cocultured model was used to analyze the gene expression of proinflammatory cytokines (IL-1β, IL-1α, and IL-6) from host cells, as well SAP-1 and PLB-1 by RT-PCR. The MIC was between 6.25 and 12.5 µM, and the activity of proteinase enzyme was significantly decreased in biofilms treated with curcumin. However, proteinase gene expression was not downregulated after curcumin treatment. Furthermore, gene expressions of host inflammatory response, IL-1β and IL-1α, were significantly downregulated after exposure to curcumin. In conclusion, curcumin exhibited antifungal activity against C. albicans and modulated the proteolytic enzyme activities without downregulating the gene expression. In host inflammatory response, curcumin downregulated IL-1β and IL-1α gene expression.